Pallet fork



May 7, 1963 J. N. SUMMERS, SR 4 PALLET FORK 2 Sheets-Sheet 1 Filed Aug.25. 1960 IN VEN TOR. Joe N Summemgbf:

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y 7, 1963 J. N. SUMMERS, SR 3,088,614

PALLET FORK 2 Sheets-She et 2 Filed Aug. 25. 1960 INVENTOR. JaeZlffiimzmers; 51:

ATTORNEYS United States Patent 3,088,614 PALLET FORK Joe N. Summers,Sr., R0. Box 909, Mission, Tex. Filed Aug. 25, 1960, Ser. No. 51,865 10Claims. (Cl. 214-653) This invention relates to a novel pallet forkattachment for an industrial truck, and more specifically to a palletfork attachment having fork members pivotally mounted and operable tograsp or clamp an article to be lifted or handled.

Most industrial trucks are equipped with a lifting device, in the formof forwardly projecting lifting forks, which are adapted to engage theunder surface of a loaded pallet to lift the pallet and the load thereonfor the purpose of moving the same to a different location.

It frequently becomes necessary to move large objects from the floor orground, such as, for example, barrels, bales of material, and the like.Attachments for industrial trucks have been suggested which involve theremoval of the lifting forks and the substitution of clamping members.This conversion is a troublesome and timeconsuming task.

It is an object of this invention, therefore, to provide an attachmentfor an industrial truck in which a pair of forwardly projecting forkscan serve either as a lifting means or as a clamping means.

A further object is to provide a combined lift and clamp attachment foran industrial truck having a pair of pivoted arms or clamping forkmembers interconnected in a novel manner for concurrent movement.

A still further object is to provide a combined lift and clampattachment for an industrial ,truck that is compact, involving a minimumnumber of parts, and which is simple in construction and reliable inoperation.

The attainment of the above and other objects will be apparent from thefollowing description when considered with the annexed drawings, inwhich:

FIG. 1 is a side elevation showing the pallet fork lift attachment ofthe present invention;

FIG. 2 is an enlarged front elevation;

FIG. 3 is an enlarged fragmentary horizontal sectional view on the line3-3 of FIG. 2;

FIG. 4 is an enlarged top plan view taken on the line 44 of FIG. 1;

FIG. 5 is a side elevational view of FIG. 4; and

FIG. 6 is a vertical sectional view taken on the line 6-6 of FIG. 2. I

Referring to the drawings, FIG. 1 illustrates a conventional industrialtruck 10 having a pair of front power wheels 12 and a pair of rearwheels 14 pivotally supported for steering by an operators steeringwheel 16. The truck also includes a brake pedal 18 and a truck controllever 20, as well as a set of control levers (not shown) for the movablecarriage and for other movable parts. The truck 10 carries, at its frontend, a mast 22 on which is mounted a vertically movable carriage 24 (seeFIG. 4), all as well known in the art.

The invention comprises a pallet fork attachment designated in itsentirety by the numeral 26, in the form of a combined lifting fork andclamping mechanism.

The attachment 26 icludes a plate member 28 (FIGS. 4, 5 and 6) which isadapted for connection with the carriage 24 by a pair of spaced capscrews 30, having non-circular heads for engagement by a suitablewrench, passing through apertures in the carriage to engage alignedthreaded bores in the plate member.

A support plate 32 is retained in parallel, spaced relation with theplate member 28 by a pair of spaced trunnions 34. The trunnions 34pivotally support a pair of fork members 36 having depending, verticallyextending,

3,088,614 Patented May 7, 1963 1 ice portions 38 and forwardlyprojecting portions 40 at the lower ends. The forwardly projectingportions 40 are parallel, at all times, and have flat upper surfacesadapted to engage the undersurface of a pallet for lifting the latter.When the depending portions 38 are brought into parallelism, as shown infull lines in FIG. 2, the upper surfaces of the portions 40 he in acommon plane. The upper ends of the portions 38 include integral bearingsleeves 42 journalled on the trunnions 34 for pivotally supporting thefork members 36 and serving as spacing sleeves to retain the platemember 28 and the support plate 32 in spaced relation. Each sleeve 42includes a first crank arm 44 and a second crank arm 46, integral withthe sleeve and angularly spaced as shown in FIG. 2 for a purpose to beset forth hereinafter.

A fluid pressure actuated servomotor 48 is connected with the forkmembers 36 for rotation thereof about the t-runnions 34. The servomotor48 comprises a cylinder 50 in which a piston 52 is caused'to reciprocatein one direction or the other by the admission and exhaust of fluidunder pressure through a pair of connections 62 and 64 on opposite endsof the cylinder. A piston rod 54 is attached at one of its ends to thepiston 52, the rod extending through an end wall of the cylinder andbeing attached, at its other end, to the crank arm 44, on one of thefork members 36, by a clevis 56. One end of a rod 58 is attached to theother end Wall of cylinder 50 and the other end of said rod is attached,by a clevis 60, with the crank arm 44 on the other fork member.

A guide support 66', in the form of an isosceles trapezoid, is securedat its base end, as by welding, to the plate member 28, the apexextending in a downward direction as seen in FIGS. 5 and 6'. The supportplate 32 is generally T-shaped and includes an integral depending leg 68forming a first guide member of a crosshead guide. The first guidemember 68 and the guide support 66 are retained in spaced relation by aplurality of bolts 70 and spacing sleeves 72. A second guide member 74,attached to the guide support 66 as by welding, is disposed in alignmentwith and in spaced parallel relation to the first guide member 68.

A crosshead, comprising a pair of bearing plates 76 joined by atransversely extending connecting plate 78 (FIGS. 2 and 3), is mountedto slide in the guideway formed by the guide members 68 and 74. As shownin FIG. 3, the bearing plates 76 are in sliding engagement with theedges of the guide members 68 and 74, while the connecting plate 78 isin sliding engagement with a face of the first guide member 68. A pairof oppositely disposed lugs 80 are made integral with the bearing plates76, as by welding. The outer ends of the lugs 80 are pivotally connectedwith the second crank arms 46 by a link system comprising links 83pivotally supported by pins 86 to the outer ends of the lugs 80, and bypins 88 with the outer ends of the crank arms 46.

It will be observed, from the foregoing, that the novel pallet fork canbe used as a lifting device in the manner of a conventional lifting forkwhen the parts are in the fluid under pressure is admitted through theconnection 62 of the servomotor 48, on the left hand side of the piston52 therein, while the fluid from the right hand side of the piston isexhausted through the connection 64, which moves the projecting portions40 of the fork members 36 into parallel relation, as shown in FIGS. 1and 4, and in full lines in FIG. 2. The fork members 36 are retained inthis position by the fluid pressure within the cylinder, and by thecrosshead, which is moved to its uppermost position, as shown in solidlines in FIG. 2. If it is desired to utilize the pallet fork as aclamping and a lifting device, the hydraulic pressure is deliveredthrough the connection 64 and drained through the connection 62, whichmoves the piston 52 in the servomotor cylinder 50 toward the left, andmoves the cylinder toward the right, swinging the crank arms 44 towardone another and simultaneously swinging the forwardly projectingportions 40 of the fork members 36 away from one another to the positionshown in broken lines in FIG. 2. The crosshead assures a synchronous andequal movement of the fork members 36. By appropriate manipulation ofthe carriage 24, the clamping and lifting attachment may be brought toany desired position, and the fork members may be maneuvered intoposition relative to the article to be clamped and lifted. When sopositioned, fluid pressure is admitted through the connection 62 anddrained through the connection 64, to bring the forwardly projectingportions 40 toward one another into a position to clamp between them anydesired article, such as a bale of cotton, hay, or straw, or any otherarticle that can be clamped. By control of the pressure admitted throughthe connection 62, which rotates the crank arms 44 and brings theforwardly projecting portions 40 toward one another, the degree ofclamping action can be controlled, while the crosshead guide assuresequal and simultaneous movement of the fork members 36.

When the article has been clamped, the entire attachment can be raisedby the carriage 24 in a manner known to the art and the article can belifted and moved to any desired location where, by control of the fluidpressure through the connections 62 and 64 of the servomotor, the forkmembers 36 can be separated or brought together as desired.

It is evident, from the foregoing, that the particular attachmentdisclosed is capable of not only functioning as a conventional liftdevice, but also as a clamping mechanism, without requiring anyreplacement of parts.

As the forwardly projecting portions 40 are always at the sameelevation, because of the crosshead connection, while being swung awayfrom or toward one another, it is evident that the forwardly projectingportions 40* can be used as a lifting fork at any position of the forkmembers 36. This is especially useful in lifting oversized articles,where it is desirable to provide a greater spacing than usual betweenthe lifting forks to assure stability during a lifting, especially incase of top-heavy articles.

It is to be understood that various changes may be made in the detailsof the pallet fork attachment disclosed herein without departing fromthe principles of the invention or from the scope of the annexed claims.

I claim:

1. A combined lifting and clamping mechanism for use with an industrialtruck having an upwardly extending mast including a carriage movablelengthwise thereof, comprising: a plate member adapted to be mounted onthe carriage; a support attached to said plate member; and

a combined lifting and clamping means mounted on said plate member,including a pair of pivotally mounted fork members, each fork memberhaving a depending portion and a forwardly projecting end portion; meansfor rotating said fork members; and additional means separate from saidmeans for rotating said fork members, acting with said support,interconnecting said fork members and being responsive to the operationof said means for rotating said fork members for effecting concurrentmovement of said fork members.

2. A combined lifting and clamping mechanism as defined in claim 1, inwhich said means interconnecting the fork members for concurrentmovement includes a guide mounted on said support, a movable crossheadsliding in cooperative engagement with said guide, and link structureconnecting said crosshead and said fork members, whereby upon operationof said means for rotating said fork members, said link structure willeffect sliding movement of said crosshead upon said guide.

3. A combined lifting and clamping mechanism as defined in claim 1, inwhich said fork members are pivotally mounted on parallel, horizontalaxes, and in which said means interconnecting the fork members forconcurrent movement includes a guide, a movable crosshead sliding incooperative engagement with said guide, and link structure connectingsaid crosshead and said fork members to assure concurrent movement ofsaid fork members in opposite directions, whereby upon operation of saidmeans for rotating said fork members, said link structure will effectsliding movement of said crosshead upon said guide.

4. A combined lifting and clamping mechanism as defined in claim 1, inwhich said means interconnecting the fork members for concurrentmovement includes a depending guide connected with said plate member andsupport and disposed between said depending portions of said fork means,a crosshead slidably supported in said guide, and link structureconnecting said crosshead and said fork members, whereby upon operationof said means for rotating said fork members, said link structure willeffect sliding movement of said crosshead upon said guide.

5. A combined lifting and clamping mechanism as defined in claim 1, inwhich said support includes a support plate parallel with and spacedfrom said plate member, trunnions retaining said plate and plate memberin spaced relation and pivotally mounting said fork members, and inwhich said means interconnecting said fork members for concurrentmovement includes a guide support attached to said plate member, a pairof parallel guide members, one of said guide members being attached tosaid guide support and the other guide member being attached to saidplate, a crosshead slidably mounted within said guide members, and linkstructure connecting said crosshead and said fork members, whereby uponoperation of said means for rotating said fork members, said linkstructure will effect sliding movement of said crosshead upon saidguide.

6. A combined lifting and clamping mechanism as defined in claim 1, inwhich the pivotal mounting for each fork member includes a lever arm,said means interconnecting said fork members for concurrent movementincluding a guide disposed between said plate member and said support, acrosshead slidably mounted on said guide, and in which the means forrotating the fork members includes a double acting fluid servomotorhaving a cylinder and a piston movable therein, and means connecting theservomotor to the lever arms for movement of the fork members, wherebyupon operation of said servomotor to rotate said fork members, saidmeans interconnecting said fork members will cause said crosshead toslide upon said guide.

7. A combined lifting and clamping mechanism as defined in claim 1, inwhich said means interconnecting the fork members for concurrentmovement includes a guide disposed between the depending portions ofsaid fork members, a crosshead slidably supported by said guide, a leverarm connected with the pivotal mount of each fork member, and a linkstructure interconnecting each lever arm and the crosshead, whereby uponoperation of said means for rotating said fork members, said linkstructure will effect sliding movement of said crosshead upon saidguide.

8. A combined lifting and clamping mechanism as de fined in claim 1, inwhich said means interconnecting the fork members for concurrentmovement includes a verti cal guide disposed between the dependingportions of said fork members, a crosshead slidably supported by saidguide, a pair of lever arms connected with the pivotal mount of eachfork member, a link interconnecting one lever arm of each pair and thecrosshead, a double acting fluid servomotor having a relatively movablecylinder and piston, and means connecting the cylinder to one lever armof said pair of lever arms and connecting the piston to the other leverarm of said pair of lever arms, whereby actuation of said lever armscon- 5 6 neeted with said servomotor will effect vertical translation10. An attachment as defined in claim 9, in which each of said crossheadupon said guide. of the fork arms has a crank arm and wherein theactuat- 9. A combined lifting and clamping attachment for use ing meansis disposed between and connected with said With a lift truck having avertically movable lifting elecrank arms.

ment, comprising: a member mountable upon said lifting 5 element; a pairof horizontally extending fork arms; References Cited in the file Ofthis Patent rfneans pivotalljy moltllnting said fork arm; on saidmgngbelrg UNITED STATES PATENTS or rotation a out orizontal axes para ewit sai or arms; actuating means connected with said fork arms to 'g s'gi simultaneously move the same; and means including a 10 2676723schggeder 1954 slide element independent of said actuating means inte-r-2683546 Shemfi 1954 connecting said fork arms and limiting the sametoequal movement by said actuating means.

1. A COMBINED LIFTING AND CLAMPING MECHANISM FOR USE WITH AN INDUSTRIALTRUCK HAVING AN UPWARDLY EXTENDING MAST INCLUDING A CARRIAGE MOVABLELENGTHWISE THEREOF, COMPRISING: A PLATE MEMBER ADAPTED TO BE MOUNTED ONTHE CARRIAGE; A SUPPORT ATTACHED TO SAID PLATE MEMBER; AND A COMBINEDLIFTING AND CLAMPING MEANS MOUNTED ON SAID PLATE MEMBER, INCLUDING APAIR OF PIVOTALLY MOUNTED FORK MEMBERS, EACH FORK MEMBER HAVING ADEPENDING PORTION AND A FORWARDLY PROJECTING END PORTION; MEANS FORROTAING SAID FORK MEMBERS; AND ADDITIONAL MEANS SEPARATE FROM SAID MEANSFOR ROTATING SAID FORK MEMBERS, COACTING WITH SAID SUPPORT,INTERCONNECTING SAID FORK MEMBERS AND BEING RESPONSIVE TO THE OPERATIONOF SAID MEANS FOR ROTATING SAID FORK MEMBERS FOR EFFECTING CONCURRENTMOVEMENT OF SAID FORK MEMBERS.